floruit
The time period during which a person, group, culture, etc. is at its peak.
Though Aristotle claimed that a human being reaches his intellectual peak at age forty-nine (Rhetoric 1390b9), chronologists reckon a person's flowering—his floruit—at about age forty. The mists of time have made the precise reckoning of chronology quite difficult. Sometimes, when a birth is not known, a floruit can be estimated on the basis of what is known about an individual's career.
Where it comes from
Unadapted borrowing from Latin flōruit (“he/she/it flourished”), from flōreō (“bloom, flourish”), from flōs (“flower”).
Adapted from the Wiktionary entry floruit (CC BY-SA 4.0).